This invention relates generally to internal combustion engines and particularly to two-cycle internal combustion engines.
Moving parts within most two-cycle internal combustion engines are lubricated by means of a fuel/oil mixture introduced into the engine's crankcase during engine operation. Although the fuel/oil mixture is in the form of a droplet cloud or mist when it is introduced into the crankcase, a portion of the mist condenses to form a lubricating film on various moving and stationary surfaces within the crankcase. The thickness of the lubricating film thus formed is dependent upon various factors such as engine and fuel temperature, the air/fuel ratio, the fuel/oil ratio, and the velocity of air flow through the crankcase.
When a two-cycle engine is shut down or stopped, residual fuel runs off the walls and other surfaces within the engine and collects at the lowest point in the crankcase. In horizontal-cylinder, loop scavenged, two-cycle engines, such as are used, for example, in marine outboard motors, a transfer passage communicating with a cylinder combustion chamber is typically provided below each cylinder. Because such a transfer passage often forms the lowest point within the crankcase, it is a likely site for the accumulation of residual fuel, and when the engine is shut down, enough residual fuel can accumulate in the transfer passage to form a significant puddle. During subsequent restarting of the engine, the accumulated puddle can be blown almost instantaneously through the transfer passage into the combustion chamber. Because the accumulated residual fuel cannot be completely burned, a noticeable cloud of smoke is produced at the engine's exhaust outlet.
In one two-cycle internal combustion engine, such as that shown in Griffiths U.S. Pat. No. 4,383,503, a segment of tubing is used in conjunction with a check valve to recirculate residual fuel from the transfer passage to the combustion chamber during engine operation in order to avoid the accumulation of residual fuel while the engine is running. This system will not, however, prevent the accumulation of a residual fuel puddle when the engine is shut down, and smoke can still be produced when the engine is restarted.
In another two-cycle internal combustion engine, such as that shown in Hundertmark U.S. Pat. No. 4,590,897, a sump is provided for collecting residual fuel from the engine crankcase, and a delivery line returns collected residual fuel to the engine when the engine is operating above a predetermined speed. However, as no provision is made for draining accumulated residual fuel from the transfer passage while the engine is shut down, smoke can still be produced as the accumulated residual fuel is blown into the combustion chamber during a subsequent engine restart.
Attention is also directed to the following U.S. patents:
______________________________________ Attention is also directed to the following U.S. Pat. Nos.: ______________________________________ 4,690,109 Ogasahara et al. Sept. 1, 1987 4,599,979 Breckenfeld et al. July 15, 1986 4,383,503 Griffiths May 17, 1983 4,359,975 Heidner Nov. 23, 1982 4,286,553 Baltz, et al. Sept. 1, 1981 4,213,431 Onishi July 22, 1980 4,181,101 Yamamoto Jan. 1, 1980 4,180,029 Onishi Dec. 25, 1979 4,176,631 Kanao Dec. 4, 1979 4,121,551 Turner Oct. 24, 1978 4,063,540 Pace Dec. 20, 1977 3,929,111 Turner, et al. Dec. 30, 1975 3,859,967 Turner, et al. Jan. 14, 1975 3,805,751 Resnick, et al. Apr. 23, 1974 3,800,753 Sullivan, et al. Apr. 2, 1974 3,762,380 Schultz Oct. 2, 1973 3,730,149 Brown May 1, 1973 3,709,202 Brown Jan. 9, 1973 3,528,395 Goggi Sept. 15, 1970 3,170,449 Goggi Feb. 23, 1965 3,132,635 Heidner May 12, 1964 3,128,748 Goggi Apr. 14, 1964 2,857,903 Watkins Oct. 28, 1958 2,781,632 Meijer Feb. 19, 1957 2,717,584 Upton Sept.13, 1955 2,682,259 Watkins June 29, 1954 2,502,968 Lundquist, et al. Apr. 4, 1950 1,733,431 Sherman Oct. 29, 1929 ______________________________________
Attention is also directed to Holtermann et al. U.S. patent application Ser. No. 105,177, filed Oct. 5, 1987 and assigned to the assignee of this application.